This invention relates to a water-dispersible epoxy modified alkyd resin and production thereof.
In recent years, attention has been given to aqueous coatings which can reduce fire risk and air pollution due to organic solvents in conventional organic solvent type coatings and can prevent the waste of resources due to the use of water as a diluent. But there are many problems to be solved in using the aqueous coatings such as drying of coating films being slow, water resistance of coating films being poor, corrosion resistance of coating films being poor, and the like.
More attention has been given to water-dispersible alkyd resins since the organic solvent content can be reduced remarkably comparing with water-soluble alkyd resins. For producing the water-dispersible alkyd resins, there have been known a method for emulsifying and dispersing by using an emulsifier, and a method for self-dispersing by imparting emulsifiability to the alkyd resin itself. The dispersing method by using an emulsifier can hardly be used practically since water resistance is reduced remarkably due to bad influence of the emulsifier. On the contrary, an alkyd resin produced by using polyoxyethylene glycol as one component of the alkyd resin without using an emulsifier as disclosed in U.S. Pat. Nos. 3,437,618 and 3,442,835 is preferable for preparing aqueous alkyd resin coatings without causing environmental pollution, since an organic solvent is scarcely used, and the amount of amines can be reduced to 50% or less of that used in a conventional water-soluble alkyd resin. But the water-dispersible alkyd resin self-dispersed as mentioned above has various defects in that water resistance and corrosion resistance of the resulting coating films are poor and drying characteristics are also poor when prepared as ordinary-temperature-curable type coatings, comparing with those of the conventional organic solvent type alkyd resin coatings and thus it is not suitable for practical use.
In order to reduce viscosity of aqueous dispersions and to improve drying characteristics when prepared as ordinary-temperature-curable type coatings, U.S. Pat. No. 3,639,315 proposes a process for producing an organic isocyanate modified water-dispersible alkyd resin.